Challenges and solutions …
smooth, continuous movement
Scripted movement in Second Life often looks jerky. This is because changing an object's position causes a 0.2 second script delay. One way to deal with this would be to use the jerkiness as a feature of how the creature moves - a lizard's legs, for example, would probably look fine with a sort of jerk-and-rest gait. For this project, though, I experimented with flexible prims as a way of masking and smoothing out the movements. Flexiprims are rendered on the client-side, meaning that the apparent movement is never calculated by the servers and so they are not subject to the same script delay as "real" prim movement. What this means in terms of visual design is that I can have tentacles which appear to smoothly flail around, even though the actual prim is moving in a jerky way (this can be seen by camming in behind the rocks and watching the plants' roots).
light
Although in SL we can change the time of day, move the sun or play for hours with the Windlight sky settings, we can't change any of these with a script, so I looked at ways to make the creatures themselves emit light. There are two ways of doing this - local lights and glow. Local lights subtly (or not so subtly) light up objects around themselves and glow lights up the object itself. Both have the disadvantage that you are never sure somebody else is seeing the same effect as they vary depending on client settings and time of day. I decided to use glow with my creatures as it's a very obvious effect and would quickly confirm that the data got through. This is why the creatures are housed in darkness - glow does not work well during daylight hours. I experimented with varying amounts of glow on different prim faces combined with almost total transparency. This worked well with the movement of the tentacles and suggested underwater creatures like jellyfish.
prim count
One of the biggest challenges to visual design within Second Life is keeping within the available prim-count for the land you have. Basically, a "prim" is a simple primitive shape such as a cube, sphere or torus. (there are also sculpties but they are of limited use). On my 512 sqm of virtual land, I can only use 117 prims altogether. Added to this, there are only a few different transformations which can be performed on a prim. The challenge was to produce something organic-looking out of as few prims as possible. Most of the creatures are 8 prims each (I experimented with using 16 and even 32 prims) and are made by simply rotating and copying the first "limb". I experimented with some using four prims - three fleshy arms and a central prim to rotate around, but I am not happy with the appearance of these yet. While an 8 prim creature is by no means excessive in SL building terms, on a 512, I rapidly ran out of prims. The choice is to delete absolutely everything on my parcel and have no more than 117 one-prim creatures in my system or to get more land. Given all the other difficulties with SL building, I have decided to go with the latter.
